Because both laboratory animals and the commonly used parameters for semen analysis are unreliable predictors of altered human male reproductive capacity, various test approaches utilizing sperm are being developed and validated. Attention is currently directed to three different approaches: (1) interspecies (human sperm/hamster ova) in vitro fertilization; (2) plant lectin interactions with heterogenous surface glycoprotein binding sites during sperm maturation; and (3) analysis of heterogenously distributed sperm surface proteins appearing during sperm maturation with monoclonal antibodies. Interspecies in vitro fertilization test results were compared with pregnancies and other clinical data of couples consulting a fertility clinic and initial results demonstrated that the test was a valid predictor of altered fertility. Research findings regarding the other two approaches are still preliminary.